Another white screen Duo issue.

[Desh]

I have been binge repairing Duo's lately.  Just finished 2 TurboDuo's with typical cap and via issues.  I just got a fairly beat up looking PCE Duo I want to save. 

Someone has already done a half cap replacement to it (and was of great workmanship) but the HuCard connector is pretty screwed and sloppily soldered back together from a likely failed region mod.  The board itself is actually in fantastic shape and appears to have been cleaned by whomever did the partial recap.  No matter what I get a solid white screen at boot up.  Here is what I have done to diagnose so far:
- Removed Hucard connector to confirm no short or other damage from attempted region mod
- Checked all power and ground pins on Huc6260, 6270 and 6280 (good)
- Noticed a bit under 5V when checking the above.  Tested 7805's and they were only outputting 4.6 and 4.8V respectively.  Replaced both 7805's and now have solid 5V

I then started poking around with my logic probe and this is where I start to get above my pay grade.  I am hoping thesteve or keith may have some advice. 

I checked all pins on 6260, VRAM and addresses for Hu slot.  I honestly don't know what I'm looking for other than some activity. 

Hu6260:

- High 1, 4, 13, 16, 21, 22, 23, 27, 28, 34, 35, 36, 41, 42, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 54, 57, 58, 59, 60, 61, 79, 80

- Low 3, 14, 15, 17, 19, 25, 29, 30, 32, 37, 39, 48, 55, 56, 67, 68, 69

- Constant pulsing 5, 6, 7, 8, 9, 10, 11, 12, 62, 63, 64, 65, 66, 70, 71, 72, 73, 74, 75, 76, 77, 78

- Nothing 18, 20, 24, 26, 31, 33, 38

HSRM20256LM12:
- 1-13 constant pulse, 15-27 constant pulse
- 14 low, 28 high (I assume 14 is supposed to be ground and 28 is VCC as I couldn't find a data sheet to confirm)

All address lines at Hu slot have a constant pulse

[thesteve]

if its always a white screen (not other colors) the HuC6270 is likely dead

[Desh]

Thank you Mr. thesteve.  I messed around with it a little more this morning before I saw your reply.  I soldered in a spare card slot from a TG (I don't have any spare Duo slots laying around) just to see if there was a change if I try and boot a card.  The only change is intermittently (about every 5th boot) I do get a purple or blue screen instead of white.

I also took the liberty of checking readings from HuC6270 and HuC6280 with the logic probe (with no card in).

HuC6270:

- High 4, 5, 6, 7, 8, 9, 10, 12, 15, 16, 17, 18, 19, 21, 22, 24, 28, 32, 39, 40, 47, 70, 72, 77, 78

- Low 11, 27, 29, 30, 31, 33, 34, 35, 36, 37, 38, 55, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76

- Pulse 1, 2, 3, 13, 14, 20, 23, 25, 26, 79, 80

- Nothing 41, 42, 43, 44, 45, 46, 48, 49, 50, 51, 52, 53, 54, 56, 57, 58


HuC6280:

- High 1, 2, 8, 11, 12, 14, 15, 19, 22, 24, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 47, 57, 59, 60, 76

- Low 7, 16, 21, 30, 48, 58, 75

- Pulse 3, 4, 5, 6, 13, 46, 49, 50, 51, 52, 53, 54, 55, 56, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 77, 78, 79, 80

- Nothing 9, 10, 17, 18, 20, 23

[thesteve]

you have an open between 6270 and 6280
half your data pins are missing on the 6270, but not 6280

[blueraven]

Wow.

This is why I love this forum. Posts and responses like this.

+5 turbokarma to you both!

[Desh]

you have an open between 6270 and 6280
half your data pins are missing on the 6270, but not 6280

Fantastic!  Thank you so much for the help.  I'll look for the source tonight after football.

[Desh]

Some progress was made.  I traced every single pin back from 6270 and had good continuity everywhere.  I even made a worksheet that mapped each pin from 6270 to their corresponding pin on 6280, 6260 and VRAM.  I couldn't find anything wrong.  For shits and giggles I plugged it back in to see if I had any change like from a loose connection etc. after I was checking the board.  To my surprise I can now boot the CD bios. 

It still won't play a disc (won't even spin up) so I haven't messed with adjusting pots but the laser won't even center so I'm leaning more towards a bad laser.  Also, I still get a blank screen when trying to boot Hu cards.  The card issue could possibly be self inflicted from removing the old slot but all of the pads are intact.  I think I will desolder that again and check those traces next.  Once I eventually get everything running I think I will be bathing this board.

[Desh]

I haven't addressed the HuCard issue yet but I continued a bit farther.  I replaced the remaining original caps (7 22uf caps, 100uf 16V, 470uf near the power switch and the 10uf near the controller port.  I swapped in a known good laser assembly from another Duo and still no centering or spindle motor even if I manually depress the "make switch" for the laser.  I tried adjusting the pots but nothing happens.  The laser itself does light but nothing else.  It appears I will be tracing back all of that circuitry as well.  Nobody has come up with a schematic of any kind for the CD portion of a Duo have they?

[blueraven]

Desh,

The only time I've ever had a CD unit fail due to hardware, I was able to re-grease the laser rails and it started moving flawlessly again. There was also a unit without power, and upon inspection revealed that a soldering Iron had gone through the teeny power wire to the CD assembly.

Have you checked the traces between the chips? Correct me if I'm wrong but I think that steve was trying to say that you have an open trace somewhere connecting the two chips. Maybe its on the 6280 side or you just have to find the one cut trace that is causing the two sides of the brain to miscommunicate.

[Desh]

Desh,

The only time I've ever had a CD unit fail due to hardware, I was able to re-grease the laser rails and it started moving flawlessly again. There was also a unit without power, and upon inspection revealed that a soldering Iron had gone through the teeny power wire to the CD assembly.

Have you checked the traces between the chips? Correct me if I'm wrong but I think that steve was trying to say that you have an open trace somewhere connecting the two chips. Maybe its on the 6280 side or you just have to find the one cut trace that is causing the two sides of the brain to miscommunicate.

When I checked I have continuity between each shared pin between 6280 and 6270.  It does boot CD bios now.  I have hypodermic test leads so I assume that I cleared some crap out of a via by accident which now has allowed the bios to boot.  I removed the card connector and there doesn't appear to be damage.  I thoroughly washed the board in warm water with dish soap and a tooth brush.  Once I'm confident that everything is dry I will continue diagnosis.

[thesteve]

the connection healed when probed
reflow the chips and try again

[Desh]

The board was good and dry from the bath.  Reflowed 6260, 6270, 6280 and the VRAM chips.  I fired it up and back to white screen again.  I do get some colors (all in the red spectrum) intermittently. 

I then got my worksheet out and checked every pin off of 6270 and had good continuity everywhere.  I then got the logic probe and checked for same signal between all pins on 6270 that are shared with 6260, 6280 and VRAM and that also checked out fine.  Then I just started reflowing every IC on the board as well as all connectors.  During the process I found the last 2 pins off the white plug for the CD drive were solder bridged.  This was not bridged on the other Duos I have here so I removed it.

CD bios booted again but still no activity or centering when trying to play a disc.  While checking some things to get the CD going the bios screen got garbled and froze.  When I tried to restart I now am back to a white screen.

It's pretty evident I have an intermittent connection issue, it's just a matter of finding it.

[blueraven]

It's pretty evident I have an intermittent connection issue, it's just a matter of finding it.

I'm out of my league at this point without being able to see the board. Could you post photos of it so we all can take a look?

Not sure if I'm even on base here but what power supply are you using? I seem to recall having a faulty power supply that created a problem like this. It wasn't putting out enough mA.

*waits patiently for steve's response*

[Desh]

It's pretty evident I have an intermittent connection issue, it's just a matter of finding it.

I'm out of my league at this point without being able to see the board. Could you post photos of it so we all can take a look?

Not sure if I'm even on base here but what power supply are you using? I seem to recall having a faulty power supply that created a problem like this. It wasn't putting out enough mA.

*waits patiently for steve's response*

I know it has enough voltage but I haven't checked for amp draw.  Would be super easy to check since the power jack isn't integrated in the board. 

I didn't even look at it last night.  I needed a break.  I have also decided that it's time I buy at least a little hot air gun to make my life easier with surface mount stuff.

[thesteve]

i didnt question the supply, as he is working multiple units